1. Field of the Invention
The present invention relates to an image encoding apparatus and method, an image decoding apparatus and method, and a program, which are able to reduce block distortion and increase encoding efficiency.
2. Description of the Related Art
In recent years, due to trends toward higher resolutions or higher frame rates of image data, it is increasingly difficult to handle numerous data using limited resources within a unit of time, in an image processing system. For example, as shown in FIG. 1, in a case where a memory 85 is used in a procedure to perform image processing using an image processing system 80, since a high-capacity memory and a wide bus bandwidth necessary for data transmission to be secured, it is difficult to miniaturize the system and to reduce costs. For example, in Japanese Patent No. 3918263, as shown in FIG. 2, an image encoding unit 81 is provided between the image processing system 80 and the memory 85 and image data is encoded before being stored in the memory so as to reduce the amount of data. In addition, an image decoding unit 82 is provided between the image processing system 80 and the memory 85 and encoded data stored in the memory 85 is decoded when being read out such that image data is obtained.
In Japanese Patent No. 3918263, differential pulse code modulation (hereinafter, referred to as DPCM) with relatively low throughput is used in an encoding method upon memory storage. For example, in data corresponding to 5 pixels (40 bits), in which one pixel has 8 bits, a first pixel is set to 8 bits and each of the second to fifth pixels is set to 6 bits by obtaining the difference between neighboring pixels and performing quantization. Accordingly, after DPCM, 32 bits are obtained by 5 pixels, thereby realizing ⅘ compression. In addition, in Japanese Patent No. 3918263, by realizing a DPCM unit by a small block unit or a bus transmission unit, it is possible to realize random access and to reduce memory capacity and bus bandwidth while maintaining the original memory access efficiency of the image processing system.